During the last years, battery-supplied portable electronic devices, such as mobile phones, digital cameras, digital video cameras, palm devices (PDA, Personal Digital Assistant) have had an increasing diffusion among users.
The success achieved by USB interfaces as connection means of personal computers (PCs) to other peripherals, such as, for example, printers, keyboards, pointing devices, memory card readers, and mass storage supports (pen drives), has induced consumer electronic devices manufacturers to provide also portable devices with such USB interfaces.
In fact, due to the growing number of multimedia functions and applications present in the portable devices which determine a high current consumption, it is necessary to frequently recharge the batteries of such devices. The USB connection ensures that such recharge occurs in a rapid manner, exploiting other portable devices.
However, a problem which is found in recharging a portable device battery by means of a USB connection is the difficulty in effectively controlling a supply current provided to the battery from the exterior through the USB connector, to prevent that such current exceeds maximum values allowed by the USB connection itself.
In order to obviate such drawback, a known solution employs a DC-DC converter having an input terminal connected to the USB connector, and provided with current detection devices associated to such input terminal. On the basis of the information provided by the above-mentioned detection devices, the converter is capable of controlling any variations from preset values of the external supply current provided to the portable device through the USB connector. Similar detection devices associated to an output terminal of the converter allow to control also variations of a charge current provided to the battery to be recharged.
However, such DC-DC converter of the known type comprises a number of discrete circuitry components which often make it too bulky and unsuitable for applications to portable devices in which, on the contrary, there is a tendency towards miniaturization and integration of the different components in order to reduce the implementation costs thereof. Furthermore, the functioning of such a DC-DC converter implies high power dissipation, which is unacceptable in many applications.